1. Field of the Invention
This invention relates to slopeboard mountings for use with tractors having a primary push blade.
2. Description of the Related Art
A slopeboard is a subsidiary blade for use with tractors having a primary push blade.
Such tractors are most commonly termed bulldozers, a term which seems to have become generic for designating a crawler-mounted tractor equipped with a primary push blade, even though the term was originally a trademark of the Caterpillar Corporation.
The slopeboard enables the tractor to cut an angle on earth adjacent to the tractor, for example, to create the slope along the side of a road that cuts through a hill.
Three patents are known to the inventors which apply to slopeboards, viz., U.S. Pat. Nos. 4,068,726; 4,079,791; and 4,223,461.
All three of these patents utilize a fluid-powered cylinder to extend and retract a rod. One end of the cylinder is attached relatively high on the back of the primary push blade, although the point of attachment for the cylinder of U.S. Pat. No. 4,223,462 appears to be somewhat lower than the point of attachment in the case of the other two patents.
The inside of the slopeboard near the edge closer to the primary push blade is rotatably attached to the primary push blade, and the free end of the rod is connected to the slopeboard farther out than the point of rotation. Therefore, extending the rod lowers the slopeboard; and retracting the rod raises the slopeboard. This works satisfactorily for the bulldozers illustrated in the three patents because such bulldozers do not have support arms for the primary push blade outside the wheels and tracks that propel such bulldozers and, consequently, relatively near the edges of the primary push blade. In fact, U.S. Pat. No. 4,079,791 explicitly declares, on lines 26 through 30 in column 2, xe2x80x9cThe sloping attachment (sometimes referred hereinafter as xe2x80x98sloper blade/board devicexe2x80x99) as shown in FIG. 1 is mounted on any six way hydraulic angle and tilt bulldozer(s), with inside the track dozer arms . . . xe2x80x9d
Larger bulldozers, however, have large arms to hold the primary push blade. These large arms are located outboard of the tracks, i.e., the plated endless belts which make contact with the ground and propel the bulldozer. In order to avoid colliding with these large arms, the hydraulic or pneumatic cylinder must be outside or above such large arms. Being outside the large arms would, though, likely subject the cylinder to damage from collisions with ground-mounted objects. Thus, a high location is preferable.
U.S. Pat. No. 3,429,380 does appear to deal with a slopeboard for a large bulldozer. The technique employed in that invention to avoid collisions between the large arms and the hydraulic or pneumatic cylinder is to have a hinge 9 attached to the edge of the primary push blade (designated mold plate 3) and to have the closed end of the hydraulic or pneumatic cylinder xe2x80x9c. . . joined by a pivotal connection 18 to the upper extremity of the hinge structure 9 . . . xe2x80x9d
The hydraulic or pneumatic cylinder is then protected by the extremely large triangular slopeboard of U.S. Pat. No. 3,429,380.
The slopeboard of U.S. Pat. No. 3,429,380 can, however, apparently not be raised significantly toward a ninety-degree position with respect to the bottom of the primary push blade; when it is not desired to use the slopeboard, the strut 33 must be mechanically disconnected before the slopeboard is swung by the hinge 9 to be alongside the bulldozer.
This leaves the hinge exposed to damage when the primary push blade is used. Such potential for damage to the hinge 9 would also occur if the slopeboard were removed, for example, because the operator of the bulldozer intended to have an extended period of operation during which the slopeboard would not be required.
The inventors have also observed an apparently unpatented slopeboard that avoids obstructions and protects the pneumatic or hydraulic cylinder by raising the cylinder as the slopeboard is raised. This device, though, creates a substantial obstruction in the field of view of the operator of the bulldozer.
A bar is pivotally attached behind but near an edge of the top of the primary push blade of the bulldozer. The closed end of a pneumatic or hydraulic cylinder is pivotally attached at an intermediate point along the bar. The rod that extends from the pneumatic or hydraulic cylinder is pivotally attached near the free end of the slopeboard; the other end of the slopeboard is pivotally attached to a long arm of the bulldozer. A first end of a link arm is pivotally attached to the slopeboard even nearer to the free end of the slopeboard than is the rod from the pneumatic or hydraulic cylinder. A second end of the link arm is pivotally attached to the free end of the bar.
As the rod is drawn into the cylinder, the free end of the slopeboard is thereby rotated upward forcing the link arm upward and rotating the bar upward, which rotation raises the cylinder. When the slopeboard is at or near the ninety-degree position with respect to the bottom of the primary push blade, however, both the cylinder and the link arm significantly obstruct the field of view for the operator of the bulldozer.
It is important to keep mounting points for the slopeboard within the width of the primary push blade in order to avoid damage to such mounting points, to have the slope board near to the edge of the primary push blade when the slopeboard has been raised to the ninety-degree position in order to minimize the risk of violating highway regulations concerning wide loads, to have the slopeboard adequately stabilized in any position, and to preclude the hydraulic or pneumatic cylinder that raises and lowers the slopeboard from striking any portion of or attachment on the primary push blade.
With respect to the bottom of the primary push blade on the tractor, the bottom of the slopeboard of the present invention can make an angle from zero degrees, i.e., even, with the bottom of the push blade to ninety degrees above the bottom of the push blade, ie., perpendicular to and above the bottom of the push blade.
When the slopeboard is at the bottom, the edge of the slopeboard is near the edge of the primary push blade and the bottom of the slopeboard is substantially aligned with the bottom of the primary push blade. Yet, when the slopeboard has been raised to the ninety-degree position, the bottom of the slopeboard is less than the height of the slopeboard from the edge of the primary push blade because of the angled support arm and because the slopeboard is so constructed and mounted to the bulldozer that the farther a point on the slopeboard is above the bottom of the slopeboard, the farther forward such a point is, thereby creating sufficient tilt that the upper portion of the slopeboard is in front of the primary push blade when the slopeboard has been raised to the ninety-degree position.
The angled support arm also permits the point of rotation to be mounted behind the primary push blade.
And, perhaps most significantly, the angled link of the Slopeboard Mounting Linkage causes the fluid-powered cylinder to be raised, and preferably moved toward the longitudinal center of the bulldozer, as such cylinder retracts the cylinder rod to rotate the slopeboard upward while minimizing obstructions to the field of vision for the operator of the bulldozer. This avoids collisions with any obstructions on the rear of the primary push blade while also keeping the mounting points behind the primary push blade.
For stability of the slopeboard, the angled link also causes the cylinder, angled link, and slopeboard substantially to create a triangular pattern when the slopeboard has been raised to the ninety-degree position, rather than having the cylinder generally in line with the raised slopeboard. And the slopeboard has three points from which it is attached to the primary push blade.